                1. Field of the Invention        
This invention relates to a method for the production of a web with good breathing properties, which is formed from at least one layer based on a mineral filler-containing plastic film, wherein the web is stretched to obtain the breathing activity of the filler-containing plastic film. This invention also relates to an apparatus for accomplishing the method.
2. Discussion of Related Art
Webs with good breathing properties based on thermoplastics, for example composite webs, have a good air and water vapor permeability. Because of only small pore sizes, they are impermeable to liquids, at the same time, because of their surface tensions and are, for example, used in the hygiene industry, the construction industry, the clothing industry, and for various other uses.
German Patent Reference DE 197 09 352 C2 teaches a web with good breathing properties, having a nonwoven web and a plastic film, containing at least one mineral filler, and applied on one side of the nonwoven web. The good breathing properties of the composite are achieved so that the mineral filler-containing plastic film is stretched either before or after joining with the nonwoven web, wherein the plastic film is stretched because of its elasticity, but not the fillers contained in it and subsequently, pores which bring about the desired good breathing properties of the plastic film are formed on the grain boundaries of the fillers. The used nonwoven web is itself permeated by a large number of pores and thus has good breathing properties and serves primarily as a reinforcement layer for the plastic film.
A generic method and a unit for the production of a web with good breathing properties is, for example, taught by European Patent Reference EP 09 50 512 A1, in which, in a first step, a precomposite is first produced from the nonwoven web on the basis of plastic filaments and/or plastic fibers and a coating of plastic film applied on one side of the nonwoven web. The precomposite is subsequently stretched in the longitudinal and transverse directions, wherein the breathing activity of the composite sheet thus produced is obtained.
One disadvantage with previously known webs with good breathing properties is increased stiffness of the web, which is inevitably obtained by the stretching and which is manifested in a good mechanical loading capacity. But at the same time, a haptic quality that is clearly more unpleasant, in comparison to textile materials, and other undesired properties, such as a rustling tendency etc., are produced. The previously known webs with good breathing properties have only a very flat, film-like structure, which is in contrast to the production of a plastic, textile-like hand, because of the necessarily high stretching of the same.
European Patent Reference EP 02 32 060 B1 teaches obtaining a plastic film with good breathing properties, containing at least one inorganic filler, such that the film is embossed by its prestretching so as to produce a rough pattern which brings about the desired formation of the pores. The plastic film produced in this manner, however, is subjected to very strong mechanical effects in its production. By itself, it has only an insufficient strength and cannot have a textile-like and thus skin-friendly hand either.